Divers are painstakingly searching the bottom of the canal, tied together, trying to cover every inch, the Lincoln County Sheriff's office said.

They have searched four miles of the canal, Chief Deputy Rollie Kramer said Thursday night. They have another 2.5 miles to go before they reach the Sutherland Reservoir.

A boat was on the reservoir Thursday afternoon, looking for something floating, and will be back on Friday, Kramer said.

Larry Sack, 61, has been missing Monday when he didn't show up at a family picnic, his daughter Shelly Byrn said. Sack suffers from diabetes.

His silver Dodge pick up was found Tuesday parked at a Nebraska Public Power District canal about six miles west of the Sutherland Reservoir, where he apparently went fishing. The line of Sack's fishing pole was in the water and his gear set out on the bank, Sheriff Jerome Kramer said.

A dive team searched Tuesday afternoon, covering about a mile and half of the canal. The swift current and hazardous underwater rip rap make it difficult, Chief Deputy Kramer said Wednesday.

The canal is approximately 15 feet deep.

Sheriff Jerome Kramer said some moss was scuffed on the banks where Sack was fishing, but it didn't conclusively indicate that a person had fallen into the water.

Kramer said the sides of the canal are dangerous, lined with solid cement and rip-rap.

Dogs were deployed Wednesday to search the surrounding area.

Sack is 6'4", weighs 250 pounds, has brown hair, blue eyes and a full beard. If anyone has information, please contact the North Platte Police Department.

Divers from Sutherland, Paxton and Keith County are conducting the search.